1. Field of Invention
The present invention relates to a structure for preventing gas leakage during inflator""s operation in an air bag system in which an inflatable air bag for use in a car is inflated by gas generated from an inflator so as to protect a crew.
The present application is based on Japanese Patent Applications No. Hei. 11-346238 and 11-347769, which are incorporated herein by reference.
2. Description of the Related Art
Generally, an air bag system has such a configuration that an inflatable air bag and an inflator for generating gas for inflating the air bag are received in a casing, and an air bag side opening portion of the casing is closed by a cover portion which has a hinge portion and a rupture presumptive portion.
Sheet metal is used for casings in most air bag systems. In some air bag systems, however, in order to take measures for environmental problems such as regulations of exhaust gas of, for example, carbon dioxide or the like, and in order to reduce the weight of a car as a whole, casing material has been changed from sheet metal to resin material. Then, the aforementioned inflator is received in an inflator receiving casing. The inflator is fixedly fastened in a predetermined position inside the casing by a bolt projected from a forward end portion of the inflator, and a nut to be screwed down to the bolt. As a structure for attaching such an inflator, there has been a proposal as shown in FIG. 18.
In this structure, fitting holes 16d and 16e in which an inflator 31 can be inserted from its front side or its rear side are provided in opposite, front and rear side walls of an inflator receiving casing 16b. 
Then, a lock flange portion 31a formed in the base end portion of the inflator 31 is locked at the outer circumferential edge of one fitting hole 16d while a bolt 33 formed in the forward end portion of the inflator 31 is attached to the other fitting hole 16e through a spacer 32. That is, a fitting flange portion 32a of the spacer 32 is engaged with the fitting hole 16e, and the bolt 33 of the inflator 31 is made to project outside through a bolt insertion hole 32b of the spacer 32. A nut 34 is screwed down to the bolt 33 so as to fixedly fasten the inflator 31 in a predetermined position.
In the aforementioned structure for attaching the inflator 31, however, when there occurs a car collision such that the inflator 31 operates to inflate the air bag 21 with gas, the reaction of the gas causes high-pressure gas to pass into a bottom portion of the inflator receiving casing 16b. As a result, the inflator 31 receives force so as to be pushed up. That is, because the inflator receiving casing 16b is formed of synthetic resin material and the spacer 32 is made of metal material, the inflator receiving casing 16b is lower in rigidity than the spacer 32. Accordingly, there occurs a phenomenon that the fitting flange portion 32a slides up while elastically deforming the circumferential edge of the fitting hole 16e. As a result, the fitting flange portion 32a of the spacer 32 is detached from the fitting hole 16e of the casing 16 as shown by the chain line in FIG. 9. Thus, there is a fear that gas leaks from a gap-between the inflator receiving casing 16b and the spacer 32 so that the inflation of the air bag 21 becomes imperfect.
On the other hand, the casing 16 made of resin material has a weld portion which is peculiar to a resin molding. That is, the weld portion is formed by branches of a resin solution which pass in a plurality of directions in a cavity so as to be brought into contact with and bonded with each other when the casing 16 is molded. Therefore, also in an air bag system in which no spacer 32 is used in an inflator receiving casing 16b with fitting holes 16d and 16e having different diameters, there is a problem that the weld portion may be broken to cause gas leakage when the inflator 31 is operated.
Further, a case of another air bag system is shown in FIG. 19.
That is, the air bag system case has a cover 101 formed integrally with an instrument panel body (hereinafter referred to as xe2x80x9cinstrument panelxe2x80x9d simply) 100, a housing 110 fitted to the cover 101, and so on. A door portion. 101c is formed in the cover 101. The door portion 101c is defined by a rupture presumptive portion 101b and a hinge portion 101a. An air bag 120 folded up and an inflator 121 for unfolding the air bag 120 are received in a space formed by the cover 101 and the housing 110. The air bag 120 is unfolded by gas generated by the inflator 121 in response to a signal from a sensor attached to a vehicle body or the like. By the unfolding of the air bag 120, the door portion 101c is opened and the unfolded air bag 120 is released to protect a crew.
In this configuration, a through hole 102 is provided in a side wall 101d of the cover 101, while a lock portion 111 is provided like a bridge on a side wall 110a of the housing 110 so as to be located in a position corresponding to the through hole 102. Then, the housing 110 is fitted to the cover 101, and the lock portion 111 of the housing 110 is engaged with the through hole 102 of the cover 101. Thus, the cover 101 and the housing 110 are locked with each other. Further, a plate 130 having an insertion portion 130a which can be partially inserted into the lock portion 111 of the housing 110 is used to hold the side wall 101d of the cover 101 between the plate 130 and the side wall 110a of the housing 110. Then, the plate 130 is fixed on the housing 110 by studs 131 and nuts 132.
When the air bag system is configured thus the movement of the cover 101 to leave the housing 110 is restricted because the insertion portion 130a of the plate 130 is inserted into the air bag system. Thus, there is no fear that the cover 101 is unexpectedly released from the locking between the through hole 102 of the cover 101 and the lock portion 111 of the housing 110.
However, there is a problem that the lock portion 111 of the housing 110 is disengaged from the through hole 102 of the cover 101 when the air bag 120 is unfolded.
That is, when the air bag 120 is unfolded suddenly, force in the direction shown by the arrows A1 in FIG. 19 acts on the side wall 101d of the cover 101. Thus, the side wall 101d of the cover 101 bulges apart from the side wall 110a of the housing 110, so that there arises a fear that the plate 130 is deformed as shown by the dotted lines in FIG. 19. When the plate 130 is deformed conspicuously like this, the restriction of the insertion portion 130a of the plate 130 on the movement of the side wall 101d of the cover 101 becomes so insufficient that there is a fear that the through hole 102 of the cover 101 is apart from the lock portion 111 of the housing 110. As a result, there is a fear that the gas generated by the inflator 121 leaks to the outside of the air bag system. In addition, there is a fear that such gas leakage results in an unfolded state of the air bag 120 different from an aimed state.
It is an object of the present invention to provide a structure for preventing gas leakage during inflator""s operation in an air bag system that can solve a new problem of gas leakage during inflator""s operation which is common to the aforementioned background art.
In order to achieve the above object, according to the present invention, there is provided a structure for preventing gas leakage during inflator""s operation in an air bag system comprising: an inflatable air bag for use in a car; an inflator for generating gas for inflating the airbag, the inflator having a flange portion and a bolt provided at a base end portion thereof and at a forward end portion thereof, respectively; a casing for receiving the air bag and the inflator; and a cover portion for covering an opening portion of the casing on the air bag side; wherein the casing is integrally constituted by an air bag receiving casing and an inflator receiving casing each of which is made of synthetic resin material; wherein a pair of fitting holes are formed in front and rear wall surfaces of the inflator receiving casing opposite to each other, so that the fitting holes are substantially equal in diameter to each other and so that the inflator can be fitted into the fitting holes; wherein one end portion of the inflator is engaged with one of the opposite fitting holes while the other end portion of the inflator is connected to the other fitting hole through a spacer; and wherein position regulating means is provided in the casing or the spacer for preventing the inflator from shifting in position.
The flange portion provided at one end portion of the inflator is preferably locked by a lock flange portion which is formed at an outer edge portion of the fitting hole, while a fitting flange portion formed in the spacer is fitted into the other fitting hole; and the bolt of the inflator is inserted into a bolt insertion hole provided in a center portion of the spacer, while a nut is screwed down to the bolt so as to fixedly fasten the inflator to the inflator receiving casing together with the spacer.
The position regulating means preferably includes the position regulating ribs integrally formed with an outer surface of the air bag receiving casing correspondingly to an outer circumferential edge of the spacer.
The position regulating means preferably includes a position regulating rib formed on an outer circumferential edge of the spacer so as to be bent to cover an outer circumferential surface of the inflator receiving casing.
The position regulating means preferably includes a position regulating rib integrally formed with an inner surface of a boundary portion between the air bag receiving casing and the inflator receiving casing so as to project from the inner surface and impose positional regulation on an outer circumferential surface of the inflator.
The position regulating rib is preferably used also as an attachment shelf plate which is formed integrally for connecting the air bag with an inner circumferential edge of a bottom portion of the air bag receiving casing.
The position regulating means preferably includes a position regulating rib formed so as to also have a function as a reinforcing rib provided correspondingly with a weld portion formed by branches of a resin solution which pass in a plurality of directions in a cavity so as to be brought into contact with and bonded with each other when the casing is molded with resin.
Further, there is provided a structure for preventing gas leakage during inflator""s operation in an air bag system comprising: an inflatable air bag for use in a car; an inflator for generating gas for inflating the air bag, the inflator having a flange portion and a bolt provided at a base end portion thereof and at a forward end portion thereof, respectively; a casing for receiving the air bag and the inflator; and a cover portion for covering an opening portion of the casing on the air bag side; wherein the casing is integrally constituted by an air bag receiving casing and an inflator receiving casing; and wherein a reinforcing rib is formed integrally with the casing correspondingly with a weld portion formed by branches of a resin solution which pass in a plurality of directions in a cavity so as to be brought into contact with and bonded with each other when the casing is molded with resin.
It is another object of the present invention to provide a case of an air bag system in which disengagement between a cover portion and a housing can be restricted even when an air bag is unfolded.
In order to achieve the above object, according to the invention, there is provided a case of an air bag system, comprising: a cover provided on a body of an interior part; a housing having a lock portion which can engage with an engagement portion of the cover; a lock holding member for holding a lock state between the housing and the cover; and deformation restriction means for restricting deformation of the lock holding member.
The deformation of the lock holding member is preferably restricted by the deformation restriction means so that the lock between the engagement portion of the cover and the lock portion of the housing is held even when an air bag is unfolded.
Preferably, the engagement portion of the cover is a through hole which is provided in a side wall of the cover; the lock portion of the housing is a bridge portion which is provided on a side wall of the housing to project therefrom; the lock holding member has a lock holding portion which can be partially inserted into the bridge portion; and the bridge portion is inserted into the through hole, while the lock holding portion is inserted into the bridge portion, and the cover is held between the lock holding member and the housing.
The deformation of the lock holding portion of the lock holding member can be restricted by the deformation restriction means even if the side wall of the cover bulges when the air bag is unfolded.
The deformation restriction means is preferably provided in the lock portion of the housing.
The deformation restriction means preferably constitutes part of the cover.
The size of the case of the airbag system can be restricted so as not to increase.
Preferably, the lock holding member is a plate.
Disengagement between the engagement portion of the cover and the lock portion of the housing can be restricted without making any large change in the lock holding member.
Preferably, an engagement protrusion portion is provided on a forward end portion of the plate.
Disengagement between the engagement portion of the cover and the lock portion of the housing can be restricted more effectively by the engagement between the engagement protrusion portion of the plate and the lock portion of the housing.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.